Bath compositions for chemical plating of metals containing boron nitrogen compounds nd an organic solubilizing compound



United States Patent BATH COMPOSITIONS FOR CHEMICAL PLATING 'OF METALSCONTAINING BORON NITROGEN COMPOUNDS AND AN ORGANIC SOLUBILIZ- INGCOMPOUND Eberhard Zirngiebl, Cologne-Flittard, and Heinz-Giinter Klein,Cologne-Deutz, Germany, assignors to Farbenfabriken BayerAktiengesellschaft, Leverkusen, Germany, a corporation of Germany NoDrawing. Filed Aug. 23, 1961, Ser. No. 133,322 Claims priority,application Germany Aug. 29, 1960 9 Claims. (Cl. 106-1) The presentinvention relates to chemical plating; more particularly it is concernedwith a process for the production of metal coatings l'y chemical means.

For chemicals plating from aqueous solutions sodium hypophosphite andalkali metal borohydride have been used until now. The hypophosphiteprocess for plating necessitates temperatures above 90 C. Thisrelatively high plating temperature limits the plating of plastics to anarrow range, since a great number of plastics, especially foils, aredeformed already at above 90 C. This is also the reason for theunsatisfactory adhesiveness of metal coatings on plastics. Furthermore,hypophosphite baths require narrow pH ranges which have to be adjustedby the addition of suitable butler substances. On the other hand, theborohydride process is carried out at low temperatures, for examplebetween 20 and 50 C., and at a pH range of 10-14, preferably in 2 Nammonia. The coatings thus obtained are strongly adherent to plasticsurfaces and their conductivity is relatively low.

The principal object of the invention is to provide a process for theproduction of metal coatings by chemical means.

Further objects will become apparent from the following description.

The objects of the invention are accomplished by treatment of theobjects to be coated with an aqueous metal salt solution and a reducingagent, said treatment consisting in that an aqueous metal salt solutionand at least one boron-nitrogen compound which carries one to threehydrogen atoms at the boron atom and at least one organic group at thenitrogen atom to act on the objects to be metallised.

BN compounds to be considered for this process are for exampleN-alkyl-borazanes and N-alkylborazoles.

The following compounds are preferably used:

(a) Borozanes, R NBH (b) Borazenes, R NBH (c) Borazines, RNBH (d)Borazoles, (RNBH) Q XNQN" triethyl borazane, N isopropyl borazene, N-

f isopropyl borazine, N trimethyl borazole etc.

Alcohols or water-soluble ethers may be used as solubilizers, forexample methanol, ethanol, dioxane, diethylleneglycol dimethyl ether andthe like.

The concentration of the metal salts used for chemical plating such asnickel, cobalt, iron-II or zinc salts, may vary within wide limits.

Due to the great number of BN compounds the plating is possible atpractically any pH value. When working in the alkaline range, the metalsare kept dissolved by suitable complex formers, for example ammonia,potassium-sodium tartrate, sodium citrate, ethylene-diamine and thelike. i

The plating temperatures comprise the range between 3,140,188 PatentedJuly 7, 1964 ice 20 and 100 C. Thus, for example, chemical plating ispossible at the following temperatures.

Reducing agent: Range "fi fg N-monomethylborazane 25-35N,N-d.imethylborazane 35-60 N-isopropylborazene 30-50N-tn'methylborazole 50-60 N,N',N"-trimethylborazane 60-80N,N',N"-triethylborazane -95 The coating obtained according to theprocess for chemical plating with BN compounds on metal surfaces such asiron, steel, copper, brass, aluminium etc. or on plastic surfaces suchas acetyl cellulose, polyglycol-terephthalate, polyacrylonitrile etc.are smooth, lustrous and adhesive.

The adhesiveness of these coatings to plastic surfaces is so strong thatthey can only be removed by destroying the plastic surface. The coatingsexhibit metal conductivity. They can be reinforced galvanically Withoutintermediate treatment.

Compared with the known processes for chemical platting, the use of BNcompounds as reducing agent for metal deposition on metal and plasticsurfaces offers the following advantages:

(a) Variety in the choice of reducing agents (b) Range of platingtemperature between +20 C. and

(0) pH range between 2 and 14 (d) Economy of the process The economy ofthe process becomes apparent when investigating the reductionequivalents. With the use of sodium hypophosphite, for example, 4-4 g.of NaH PO are required per reduction equivalent; with the use of N-monomethyl borazane there are required 7.5 g. of CH NH BH withN,N'-diethyl-borazane, 14.5 g. of (C H NHBH Since mixtures of anhydrousmetal salts and B-N compounds do not react with one another, thesemixtures can be marketed. The desired plating bath is obtained byintroducing such a mixture into water.

The following examples are given for the purpose of illustrating theinvention.

Example 1 A foil of polyglycol-terephthalate is consecutively pretreatedin the following baths:

(a) 200 g. of sodium hydroxide+0.5 g. of an alkyl sulfonate of theMersolate type+800 g. of water; duration of stay, 5 minutes;temperature, 50-60 C.

(b) 100 g./litre of zinc (II) chloride+200 cc./litre of concentratedhydrochloric acid+0.5 g./litre of an alkyl sulfonate of the Mersolatetype; duration of stay, 5 minutes; temperature, 50-60 C.

(c) 0.5 g./litre of palladium chloride+10 cc./litre of concentratedhydrochloric acid; duration of stay, 5 minutes; temperature, 20-30 C.

The chemical plating is carried out in a borazane bath of. the followingcomposition:

45 g./litre of nickel chloride 5 g./litre of cobalt chloride cc./litreof a concentrated ammonia solution 1 g./litre of N-methylborazane 50cc./litre of methanol The bath temperature is 25-35 C., the duration ofstay is .5 minutes. A silvery coating is thus obtained having aresistance of 0.2 to 0.5 ohm/cmP.

A coating of equal properties is obtained if N-methylborazane isreplaced by N-ethyl-borazane.

Example 2 A foil of acetyl cellulose is subjected to a pretreatment inthe baths:

(a) 100 g. of sodium hydroxide+0.5 g. of an alkyl sulfonate of theMersolate type+900 g. of'water (b) and (c) as in Example 1 Example'j Afoil of cellulose acetobutyrate is subjected to the pre-treatment ofExample 2 and chemically plated in a bath of the following composition:100 g./litre of nickel sulphate, g./litre of N,N',N"-trimethyl-borazane,1.0 cc. of N/l hydrochloric acid, 30 cc./litre of tertiary butanol.

The bath temperature is 6080 C., the pH value is 4.5, the duration ofstay is 5 minutes. coating is thus obtained with a resistance of 0.8ohm/ cm.

Example 4 100 g. of nickel sulphate are dissolved in 500 cc. of waterand 400 cc. of methyl alcohol and 3 g. of N-ethylborazane are addedthereto. A strongly adhesive compact nickel coating is obtained on acopper sheet introduced 'into the solution heated to 50-60 C.

Example 5 100 g. of cobalt sulphate are dissolved in 500 cc. of waterand a solution of 3 g. of N,N-diethyl-borazane in 500 cc. of methanol isadded thereto. A brass sheet is suspended in this solution heated to6070 C. A strongly'adhesive cobalt coating is formed on the brass sheet.Coatings on copper and iron can be produced in the same solution.Plastics can likewise be plated in this solution after a suitablepre-treatment.

Example 6 V 100 g. of nickel sulphate are dissolved in 500 cc. of water,and 500 cc. of methanol and 3 g. of N,N-diethy1- borazane are addedthereto. After preliminary treatment as described in Example 1 or 2,iron, brass, copper and plastics can be provided at 6070 C. with astrongly adhesive nickel coating.

Example 7 50 g. of nickel sulphate are dissolved in 500 cc. of water and250 ml. of diethylene-glycol dimethyl ether (Diglym) and 5 g. ofN,N',N"-triethyl-borazane are added thereto. The pH value is adjusted to2-4 with acid. A suspended copper sheet is coated at 85-95" C. with astrongly adhesive nickel layer.

Example 8 A polyglycol-terephthalate foil is pre-treated as described inExample 1 and chemically plated in a bath of the following composition:g./litre of iron (H) sulphate, 100 g./litre of sodium citrate, 30g./litre of nickel sulphate, 60 gf/litre of Seignette salt, 3 g./litreof N,N- dimethyl-borazane, 50 cc./litre of methanol.

The pH value is adjusted to 89 with sodium hydroxide solution, thetemperature is 6070 C. An iron-nickel coating is thus obtained whichadheres strongly to the foil. Iron, brass and copper can also bechemically plated in the same bath. The coat contains about 70% of iron.

Silvery metal Example 9 An iron, copper and brass sheet having thedimensions 50 mm.x mm. is introduced, after degreasing, into a bath ofthe following composition: 30 g./litre of iron (II) sulphate, 10g./litre of cobalt sulphate, 50 g./litre of Seignette salt, 2 g./litreof N,N-dimethyl-borazane, 50 cc./litre of ethanol.

The pH value is adjusted to 810 with a sodium hydroxide solution, theplating temperature is 80-90 C. An adhesive iron-cobalt coating isobtained on all plates. Plastics can also be chemically plated in thesame bath after a preliminary treatment as described in Example 1.

Example 10 (a) 5 g. of nickel sulphate, 5 g. of cobalt chloride, 5 g. ofammonium chloride and 5 g. of zinc chloride are dissolved in water. 160cc. of a concentrated ammonia solution are added thereto and the mixtureis made up to l'litre with water. After the addition of 2 g. ofN,N'-dimethyl-borazane and 50 cc. of dioxane, copper, iron, brass andplastics can be coated with an adhesive Ni-Co-Zn layer after preliminarytreatment as described in Example 1.

(b) Nickel-zinc coatings are obtainedfrom a bath of the followingcomposition: 5 g./litre of nickel chloride, 5 g./litre of zinc chloride,5 g./litre of ammonium chloride, 160 cc./ litre of concentrated ammonia,l-2 g./litre of N-monoor N,N'-dimethyl-borazane, 50 cc./litre ofmethanol. The bath temperature is 4060 C. The coatings contain up to 20%of zinc.

Example 11 In a bath of the following composition: 50 g. of nickelsulphate, 500 ml. of water, 500ml. of methanol, 2 g. ofN,N-dimethyl-borazane, plastics, copper, iron and brass can be platedadhesively at pH 5-6 and a temperature of 35-45 C. after preliminarytreatment as described in Example 1. I

N,N'-dimethyl-borazene is prepared by heating dimethyl-borazane under anitrogen stream at 400 mm. Hg and C. The analysis corresponds todimethyl-borazane.

Example 12 .Iron, copper, brass and plastics can be chemically plated soas to be adhesive at pH 5-6 and 3040 C. in a bath of the followingcomposition: 50 g. of nickel sulphate, 500 cc. of water, 500 cc. ofmethanol, 12 g. of a mixture of N-isopropyl-borazane andN-isopropylborazine.

Chemical plating with a borazene-borazine mixture can also be carriedout from ammoniacal baths at a temperature between 30 and 50 C.: 25 g.of cobalt chloride, 25 g. of nickel chloride, cc. of ammonia, 750 cc. ofwater, 12 g. of a mixture of N-isopropyl-borazene andN-isopropyl-borazine, 100 cc. of methanol.

Example 13 100 g. of nickel sulphate are dissolved in 500 cc. of water,500 cc. of methanol are added thereto and the mixture is heated to 50 C.After the addition of about 2-3g. of N-isopropyl-borazine, plastics,brass, iron and 7 copper can be chemically plated.

N-isopropyl-borazine is obtained by further heating of thebenzene-borazine mixture used in Example 12. The analysis corresponds toa 99% N-isopropyl-borazine.

Example 14 (a) 100 g. of nickel sulphate are dissolved in 500 cc. ofWater, 500 cc. of methanol are added and the mixture is heated to 5060C. After the addition of 2 g. of N- trimethylborazol copper, iron, brassand pre-treated plastics can be chemically plated.

(b) 25 g. of cobalt chloride and 25 g. of nickel chloride are dissolvedin 700 cc. of water. After the addition of 200 cc; of dioxane and 2 g.of N-trimethylborazole, pre-treated plastics, iron, brass and copper canbe chemically plated at 5060 C.

N-trimethyl-borazole is obtained by heating N-monomethyl-borazane to 120C. under a nitrogen stream at 400 mm. Hg. The analysis corresponds toN-trimethylborazole.

We claim:

1. A bath for the plating of metal and plastic surfaces by chemicaldeposition, comprising an aqueous solution of at least one metal saltselected from the group consisting of cobalt, nickel, iron II and zincand at least one boron nitrogen compound selected from the groupconsisting of:

(a) borazanes of the formula R NBH (b) borazenes of the formula R NBH(c) borazines of the formula RNBH (d) borazoles of the formula (RNBl-Dwherein R is selected from the group consisting of alkyl, aryl,hydrogen, and wherein at least one R is of the group alkyl and aryl, andorganic compound solubilizing the boron nitrogen compound in the aqueousmedium and selected from the group consisting of alcohols andwatersoluble ethers, the said boron nitrogen compound being a reducingagent in said solution in a pH range from 2 to 14 and at a temperaturerange from 20 to 100 C.

2. A bath as claimed in claim 1, wherein the plating bath contains 50grams of nickel sulfate, 500* ml. of water, 500 ml. of methanol, 1 to 2grams of a mixture of N- isopropyl borazane and N-isopropyl-borazine,the bath having a pH value between 5 to 6 and a temperature between 30and 40 C.

3. A bath according to claim 1, wherein the plating bath contains 25grams of cobalt chloride, 25 grams of nickel chloride, 160 ml. ofammonia, 750 ml. of water, 100 ml. of methanol and 1 to 2 grams of amixture of N-isopropyl borazane and N-isopropyl borazine.

4. A bath according to claim 1, wherein the plating bath contains 100grams of nickel sulfate, 500 m1. of water, 500 ml. of methanol, 2 gramsof N-trimethyl borazole.

5. A bath for the plating of iron, brass and copper which bath contains25 grams of cobalt chloride, 25 grams of nickel chloride, 700 m1. ofwater, 200 ml. of

6 dioxane and 2 grams of N-trimethyl borazole, the bath having atemperature between and C.

6. A bath for the plating of brass, copper and iron which contains 100grams of cobalt sulfate, 500 ml. of water, 500 ml. of methanol, 3 gramsof N,N-diethyl borazane, the bath having a temperature between 60 and C.

7. A bath for the plating of metal and plastic surfaces by chemicaldeposition, comprising an aqueous solution of at least one metal saltselected from the group consisting of cobalt, nickel, iron II and zinc,and at least one boron nitrogen compound selected from the groupconsisting of:

(a) borazanes of the formula R N-BH (b) borazenes of the formula R N--BH(c) borazines of the formula RNBH (d) borazoles of the formula (RNBH)wherein R is selected from the group consisting of lower alkyl having atleast 2 carbon atoms, aryl, and hydrogen, and wherein at least one R isof the group alkyl and aryl, and an organic compound solubilizing theboron nitrogen compound in the aqueous medium and selected from thegroup consisting of alcohols and water-soluble ethers, the said boronnitrogen compound being a reducing agent in said solution in a pH rangeof from 2 to 14 and at a temperature range of from 20l00 C.

8. A bath according to claim 1 wherein the boron nitrogen compound is awater-insoluble borazane.

9. A bath according to claim 7, wherein the boron nitrogen compound is awater-insoluble borazane.

References Cited in the file of this patent UNITED STATES PATENTS2,461,661 Schlesinger et al. Feb. 5, 1949 2,942,990 Sullivan June 28,1960 2,990,296 Hoke June 27, 1961 3,062,666 McLeod Nov. 6, 19623,063,850 Mikulski Nov. 13, 1962 OTHER REFERENCES Hurd: Chemistry of theHydrides (1952), pub. by John Wiley and Sons, Inc. pp. 77 and 84 reliedon.

o UNITED STATES PATENT OFFICE (-IERTIFICATEv OF CORRECTION July T 1964Patent No.: 3,,l40 l88 Eberhard Zirngiebl et alg he above numberedpatpears in t Patent should read as rtifi ed that error ap (1 Letters Itis hereby ce tion and that the sen.

ent requiring correc corrected below.

Column 4, line 64 for "benzeneborazine" read bOIHZGDBbOIHZiDe -u Signedand sealed this 10th day of November 1964,-

(SEAL) Attest:

EDWARD J.. BRENNE ERNEST W. SWIDER' Attesting Officer Commissioner ofPatent

1. A BATH FOR THE PLATING OF METAL AND PLASTIC SURFACES BY CHEMICALDEPOSITION, COMPRISING AN AQUEOUS SOLUTION OF AT LEAST ONE METAL SALTSELECTED FROM THE GROUP CONSISTING OF COBALT, NICKEL, IRON II AND ZINCAND AT LEAST ONE BORON NITROGEN COMPOUND SELECTED FROM THE GROUPCONSISTING OF: (A) BORAZANES OF THE FORMULA R3N-BH3 (B) BORAZENES OF THEFORMULA R2N-BH2 (C) BORAZINES OF THE FORMULA RN-BH (D) BORAZOLES OF THEFORMULA (RH-BH)3 WHEREIN R IS SELECTED FROM THE GROUP CONSISTING OFALKYL, ARYL, HYDROGEN, AND WHEREIN AT LEAST ONE R IS OF THE GROUP ALKYLAND ARYL, AND ORGANIC COMPOUND SOLUBILIZING THE BORON NITROGEN COMPOUNDIN THE AQUEOUS MEDIUM AND SELECTED FROM THE GROUP CONSISTING OF ALCOHOLSAND WATERSOLUBLE ETHERS, THE SAID BORON NITROGEN COMPOUND BEING AREDUCING AGENT IN SAID SOLUTION IN A PH RANGE FROM 2 TO 14 AND AT ATEMPERATURE RANGE FROM 20 TO 100*C.